1. Field of the Invention
This invention relates to novel sunscreen compositions which, when applied to the human skin provide protection against the harmful effects caused by ultraviolet radiation. More particularly, this invention relates to sunscreen compositions in the form of oils, lotions, creams, aerosols and gels wherein an ultraviolet light-absorbing ingredient is placed on the skin and is provided with increased water resistant characteristics with the aid of a polymeric binder. Most particularly, this invention relates to sunscreen compositions that are water-proof and fulfill the guidelines established by the Food and Drug Administration, as listed in the Federal Register: Volume 43, Number 166.
2. Discussion of the Relevant Art
Sunscreen compositions are commonly used during outdoor activity. Many people have occupations which require them to be exposed to the sun for long periods of time. Others choose to use their free time in outdoor recreations e.g. sunbathing, playing golf, surfing, fishing, skiing and swimming. All of these activities promote perspiration or allow the body to come in contact with water. Numerous sunscreen compositions have been developed which absorb ultraviolet light in a region of 280 to 320 nanometers (2800-3200 Angstroms; referred to as the "erythemal region") to protect the human body against this radiation that produces erythema and skin cancer, whether the source be from the sun or from man made devices. These compositions also incorporate ultraviolet absorbing agents that absorb in the region between 320 and 380 nanometers (3200-3800 Angstroms) and should be resistant to removal from the skin by perspiration or water in order to broaden and prolong their effectiveness.
Numerous substantive sunscreen agents, and substantive and water-resistant sunscreen compositions are available today. Development of substantive sunscreen agents and sunscreen compositions containing these substantive agents are illustrated in U.S. Pat. No. 3,864,473 issued to Ciaudelli; U.S. Pat. No. 4,004,074 issued to Gerecht; and U.S. Pat. No. 4,256,664 issued to Epstein. These compositions make use of sunscreen agents that are not approved by the FDA and their topical use is limited.
No known sunscreen agent, that achieves a degree of water-resistancy, has been approved by the Food and Drug Administration. FDA approved sunscreen agents have, however, been incorporated into compositions which upon application to the skin physically keep the sunscreen agent on the skin during perspiration or immersion in water. The majority of these compositions make use of polymeric materials that are either emulsified in the composition or carried to the skin by a vehicle in which a continuous polymeric film is cast on the skin.
The use of an acid form of a cross-linked co-polymer of ethylene-maleic anhydride composition in the form of a gel is illustrated in U.S. Pat. No. 3,821,363 issued to Black. Compositions and methods are described in U.S. Pat. No. 3,895,104 issued to Karg in which polyamide resinous material is used as a film former. The use of acrylate/acrylic acid copolymer compositions in the form of oils and emulsions are illustrated in U.S. Pat. No. 4,172,122 issued to Kubik. In U.S. Pat. No. 4,254,102 issued to Kaplan there is described the use of compositions containing hydroxyethyl-cellulose in conjunction with a surface active agent and a fatty alcohol. In U.S. Pat. No. 4,193,989 issued to Teng, there are described gel compositions of hydroxypropyl cellulose acetate as the film former.
Known compositions that make use of polymers to form a continuous polymeric film in which the active sunscreen agent is homogeneously dispersed throughout the matrix of the film have numerous disadvantages. Aqueous based compositions in which the polymer is usually emulsified have long drying rates on the skin, foam on the skin during application and during the drying cycle leave the skin feeling tacky. These compositions, if not fully dried, also have a tendency to allow particulate matter, such as beach sand, to adhere to the skin. Furthermore, the water-resistant properties of these aqueous based compositions are decreased if they are not fully dried before perspiration or entry into water. The formation of a continuous protective film on the skin is prevented by compositions which make use of solvent systems because they cannot tolerate large amounts of oil and other emollients. Without the use of emollients in compositions containing alcohols, the skin may become dry and irritated. Generally these compositions are also formulated in thin solutions with low viscosities which make them difficult to apply to the skin in an even manner.
Compositions, which make use of an ethylcellulose polymer in combination with ethanol as a solvent and are effective in resisting water wash off, are illustrated by Fourman in U.S. Pat. No. 4,559,225. These compositions, however, are limited to ingredients that are compatible with ethanol. They are also difficult to apply to the skin evenly thus permitting spot burning to occur, which may result in extreme pain and blistering of the skin. This effect is more pronounced with individuals having fair complexions and who normally use sunscreen products having high SPF (Sun Protection Factor) values. Water resistant compositions described heretofore that contain high levels of ethanol in combination with a polymer, that are currently being marketed, in addition to being difficult to apply to the skin evenly, produce a high degree of tack to the skin after immersion in water. This inherent negative effect usually lasts until the skin is fully dried, leaving the user in a very uncomfortable situation.
Furthermore, compositions having high ethanol concentrations lack the ability to be homogeneously combined with highly non-polar compounds such as mineral oil.
The present invention overcomes the shortcomings of known water-resistant sunscreen compositions by incorporating ingredients that resist removal of the active sunscreen agent by perspiration and water when applied to the skin. The present invention, in combination with ingredients that allow the composition to be ethanol free in nature, that can be applied to the skin evenly and easily, that protect the skin from the harmful effects of the sun's radiation, also prevent the skin from drying without leaving the skin feeling tacky. There is a need for such a product for both health and cosmetic reasons. Ingredients may be available which exhibit one or more of these desired attributes but the combination of these attributes, for use in preparing water-proof sunscreen systems has not been demonstrated. Ingredients fulfilling these requirements, which have not been used previous to this invention in water-proof sunscreen compositions are the combination of active sunscreen agents and ethyl hydroxyethyl cellulose polymers.